It is known that the deterioration of an electricity storage device progresses when the charge and discharge due to high current occur or the frequency of the charge and discharge is high. For example, Patent Literature 1 discloses that an engine control device of a hybrid vehicle detects the traveling state of the vehicle on the basis of the required power or the like required for vehicle traveling. Here, the required power is determined on the basis of various detection signals of the operation state of an accelerator pedal or brake pedal and the vehicle driving state such as the vehicle speed. In this disclosure, when the detection result indicates the traveling state in which the load variation of the vehicle is a predetermined value or more and the required power greatly varies, the vehicle is controlled so as to absorb the variation in the required power with the operation output of the engine, and hence the charge and discharge of the battery at a high power are suppressed.
Patent Literature 2 discloses that, in the control method of a hybrid vehicle, idle rotation is performed without stopping the engine in the case that the required power of the vehicle is lower than a threshold and the vehicle speed is low but is a threshold or higher. In this disclosure, in order to enable the engine to speedily respond to a rapid change of the required torque, the idle speed is increased with the increase in the vehicle speed, and hence the rapid change of the charge/discharge power of the battery is prevented to suppress the deterioration.